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About the Map

The shaded polygons in the map above represent Maryland’s 12-digit scale watersheds. The delineation breaks the state up into 1,100+ watersheds. Thus, these watersheds are smaller in size than the 8-digit scale watersheds and generally represent drainage divides between 2nd order rivers/streams. These watersheds are identified via a 12-digit numeric code. Watersheds in this polygon file relate to TMDLs and WLAs in the applicable queries via a 12-digit watershed name identified in the location description, if applicable (i.e., if the TMDL/WLA is developed at a 12-digit watershed scale).

Related Maps

Chesapeake Bay TMDL Map:  The 58 nitrogen TMDLs that comprise the Chesapeake Bay TMDL>

How to Use the Map

Clicking on a shaded polygon will display information about that 12-digit watershed, including the watershed name and ID.

To navigate the map, use your arrow to drag and pan. Click the plus and minus buttons to zoom in and out. Enter an address in the window (top right) to zoom to a location. Clicking on "Basemap" allows the user to change the background (e.g. aerial photography, topographic coverage, etc). Clicking on “View Larger Map” will take the user to a customizable map interface where additional layers may be added.

Please direct questions or comments concerning Maryland's TMDL Program to mde.tmdlcoordinator@maryland.gov at (410) 537-3818.​​